Art attack: political graffiti from the 1970's

There was a time when graffiti artists did something other than write their own names on other people's walls. Back in the '70s, graffiti had a political purpose and - whisper it - a conscience. A new exhibition at The Horse Hospital (open until Aug 1) is showing brilliantly angry political daubings from that era, from Roger Perry's recently republished book 'The Writing on the Wall'. Check out more of this polemical sloganeering (and Eric Clapton worshipping) here.